Sequestration is the process of pulling carbon out of the atmosphere and storing it somewhere safe where it will not escape and contribute to climate change.
Reducing the amount of carbon currently in the atmosphere is a necessary part of stopping climate change. Major changes need to happen to stop further emissions from contributing factors like fossil fuels and deforestation. Yet simply preventing further emissions is not sufficient to prevent global temperature rises.
We already have too much carbon in the atmosphere – in June 2011, atmospheric carbon concentrations reached 393.29 parts per million (ppm), well above the ’safe’ level of 350 ppm, or the pre-industrial level of 280 ppm. That is why sequestration is a part of the solution to climate change – because it pulls excess carbon from the atmosphere and stores it safely.
Sequestration can happen in a couple of different ways. Biochar is one technique, where carbon is stored in organic matter and frozen into long-lasting charcoal and stored in the soil. Another method of sequestering carbon is simply by growing trees. Long-term reforestation draws carbon from the air into plant material. That is why forests and biochar are used as carbon offsets in emissions trading schemes.
The most commonly debated type of sequestration is geosequestration, also called ‘carbon-capture-and-storage’. This involves capturing the emissions from concentrated sources, usually fossil fuel plants, and storing the greenhouse gases underground in the form of stable gases or liquids. This is sometimes called ’scrubbing’ the atmosphere of carbon emitted by fossil fuel plants, which is how the term ‘clean coal’ emerged.
If coal really could be cleaned up, it would be a great gift for our economies, which benefit from the cheap energy that coal provides, as well as to the workers in the coal industry that rely on it for employment, and to the governments that benefit from coal company donations. Clean coal would mean business as usual, a way of cutting the emissions from fossil fuels without having to change our way of life.
That all sounds great! What could be wrong with cleaning up a bit of coal?
Well, one insurmountable problem is the fact that clean coal does not exist commerically. The technology is at least two decades and many tens of billions of dollars in research away from commercial operation. So even if carbon capture and storage sounds great in theory, there is no practical evidence that it is a real solution to climate change.
That means that geosequestration could definitely help us tackle future emissions from fossil fuels, but that option is a long way off. While we can continue to invest in research into carbon capture and storage, other sequestration solutions like reforestation and biochar already exist, as do alternatives to fossil fuel energy, such as wind and solar power.
Co2 Now, ‘Annual Co2’, http://co2now.org/index.php?option=com_content&task=view&id=171&Itemid=1
350, 350 Science, http://www.350.org/about/science
Shein, K.A., ‘State of the Climate in 2005’, Bulletin of the American Meteorological Society, June 2006 (87), http://www.ncdc.noaa.gov/oa/climate/research/2005/ann/annsum2005.html
BBC News, ‘Clean coal technology: How it works’, 28 November 2005, http://news.bbc.co.uk/2/hi/sci/tech/4468076.stm
Fred Pearce, ‘Greenwash: Why ‘clean coal’ is the ultimate climate change oxymoron’, The Guardian, 26 February 2009,http://www.guardian.co.uk/environment/2009/feb/26/greenwash-clean-coal